Coral Records at the Northern Edge of the Western Pacific Warm Pool Reveal Multiple Drivers of Sea Surface Temperature, Salinity, and Rainfall Variability Since the End of the Little Ice Age

Abstract

Reconstructions of key climate parameters prior to anthropogenic influences serve to constrain decadal to multicentury natural climate variability. In the western Pacific region, relatively few reconstructions exist north of the Western Pacific Warm Pool (WPWP), a region critical to global climate. In this study, we collected a coral core from Houbihu, southern Taiwan, and generated a 225-year reconstruction of annual and wintertime sea surface temperature, dry season sea surface salinity, and wet season rainfall records derived from paired Porites Sr/Ca and δ 18 O profiles extending back to the end of the Little Ice Age (1850 CE). Multidecadal sea surface temperature trends generally track regional surface temperature reconstructions, indicating the dominant influence of solar and volcanic radiative forcings. Reconstructed dry season sea surface salinity reflects an advection signal linked to the East Asian Winter Monsoon and the Pacific Decadal Oscillation, both influencing variations in the Kuroshio Intrusion across the Luzon Strait. Reconstructed wet season rainfall, on the other hand, reveals influence of the Pacific Decadal Oscillation on the decadal variability of local and regional rainfall patterns. Relative to the late 1900s, our climate reconstructions document cooler and drier (high salinity and low rainfall) conditions during the end of the Little Ice Age, supporting other lines of evidence of a retracted WPWP region during this period. In the late 20th to early 21st century, our climate reconstructions record warming and freshening (low salinity and high rainfall) trends, highlighting the potential impact of anthropogenic forcing in the extension of the WPWP.

Natural and Anthropogenic Forcing of Multi‐Decadal to Centennial Scale Variability of Sea Surface Temperature in the South China Sea

“…S. Wang et al, 2011). One critical tool for paleoclimate reconstructions is the inverse relationship between SST and the concentration of strontium (Sr) relative to calcium (Ca) in the coral skeleton (Beck et al, 1992;Smith et al, 1979;Weber, 1973), which has been used successfully to reconstruct SST at seasonal-to-multidecadal frequencies from corals around the world (e.g., Carilli et al, 2014;Cole et al, 1993;DeLong et al, 2014;Goodkin et al, 2008;Hughen et al, 1999;Kilbourne et al, 2010;Ramos et al, 2020).…”

Drivers of Coral Reconstructed Salinity in the South China Sea and Maritime Continent: The Influence of the 1976 Indo‐Pacific Climate Shift

“…Published coral‐based salinity records located in the SCS and MC were identified for analysis based on the following criteria: (a) their δ 18 O coral data was publicly available, (b) the data had a sub‐seasonal resolution, and (c) the δ 18 O records were converted to sea surface salinity (SSS) to ensure that only data capturing a salinity signal are examined. Five coral records met the selection criteria (Murty et al., 2017, 2018; Ramos, Goodkin, Druffel, et al., 2019; Ramos et al., 2020, 2017; Ramos, Goodkin, Siringan, et al., 2019); the coral locations are shown in Figure 1 and additional information on the records are given in Table 1. Calibrations and validity of the previously published salinity records can be found in Supporting Information (Figure S2 in Supporting Information ).…”

“…These also correspond to the respective dry and wet seasons in the southern Indonesian archipelago (Murty et al., 2017, 2018). The seasons for Palaui (Ramos, Goodkin, Druffel, et al., 2019; Ramos, Goodkin, Siringan, et al., 2019) and Houbihu (Ramos et al., 2020) similarly correspond to boreal winter and summer but they average slightly longer periods, December–March (DJFM) and June–September (JJAS) respectively.…”

“…The coral records used in this study are located at major channels of inflow and outflow for the SCSTF and ITF (Figure 1). Two sites, Houbihu and Palaui, encompass the northern and southern edges of the Luzon Strait (Ramos, Goodkin, Druffel, et al., 2019; Ramos et al., 2020, 2017; Ramos, Goodkin, Siringan, et al., 2019). Advected waters from the SCS into the Makassar Strait are recorded by the Doangdoangan Besar coral (Murty et al., 2017).…”

“…Several salinity reconstructions exist for the MC and SCS (Murty et al., 2017, 2018; Ramos, Goodkin, Druffel, Fan, & Siringan, 2019; Ramos et al., 2020, 2017; Ramos, Goodkin, Siringan, & Hughen, 2019). Each site identifies different local drivers of salinity consistent with our knowledge of the major climate drivers in the MC and SCS regions.…”